Field pipelines: types, operation, GOST

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

To transport the produced oil from the well to the central collection point, field pipelines are needed. They are also designed to move "black gold" to other objects within the framework of the fishery. Field pipelines, depending on the pressure, can be divided into three types: high pressure, medium pressure and low pressure. They can also be simple when there are no branches, and complex - with branches. The method of laying field pipelines also divides them into underwater, aboveground, surface and underground.

Destination dependencies

Field pipelines can be non-pressure and pressure. The division does not end there. For example, pipelines are discharged when oil is pumped to the installation from a well according to the measurement: the diameter of the pipe, depending on the productivity of this well, is 75-150 millimeters. Field technological pipelines are also needed. Prefabricated collectors are designed to transport oil to the installation, where oil is prepared: gas, mineral s alts, water are removed from it. The diameter of such collectors is 100-350 millimeters.

Field gas pipelines collect gas, field inhibitor pipelines supply reagents to wells, field water pipelines supply water to support the formation. And for all this, pipes are needed. The installation conditions (for example, the terrain) suggest, when designing field pipelines, which type is best used in this particular case. In gravity flow, oil moves by gravity under the influence of gravity, in pressure-gravity flow only oil can be pumped, free-pressure pumps distill separately oil, separately gas. But there are also combined types.

In addition, field oil pipelines, depending on the installation conditions (for example, on the presence / absence of slopes of the relief) are divided into the following types: - gravity (movement occurs under the action of gravitational forces); - pressure-gravity (only oil); - free gravity / non-pressure (oil and gas move separately from each other); - combined. When constructing field pipelines, all this must be taken into account.

If the oil is heated, it becomes more viscous, then the speed of its movement through the pipe increases significantly. This is used when pumping large quantities of oil. The difference between the main and field pipelines is that the latter deliver the mineral no further than the processing enterprise, this is its end point. And the main ones - all over the world. Nevertheless, the construction of field pipelines is indispensable, this is the most important component for collecting oil and itscommodity preparation, water and gas supply for the RPM system.

Field pipelines built for technical needs and according to technological rules transport the produced products from the wellhead to the head main structures of gas and oil pipelines or to the gas processing plant (refinery). It is also necessary to construct pipelines for supplying water produced by the process - from the CPF and the UPSV to the sewage pumping station, and then from there to the field - its injection wells. Oil and gas production is distinguished by the use of rather complex technologies; many research institutes are closely working on the development of pipelines and related mechanisms.

Operation of field pipelines

In order to increase the capacity of prefabricated reservoirs when new wells are connected or the productivity of the old ones is increased, it is necessary, as already mentioned, to reduce the viscosity and warm up the oil. There are other ways: watered oil is then introduced, a parallel oil collector (looping) is laid, or an additional pump is connected in parallel.

Main and field pipelines through which commercial oil is transported (when the saturated vapor pressure is not higher than 500 millimeters of mercury (66.7 kPa) at +38 degrees, are usually called oil pipelines. And if products from oil wells are transported along with gas that is dissolved or is in a free state, and the saturation pressure of oil vapor is absolute at +20 degrees, such pipelines are calledoil and gas pipelines. If produced water is transported, it is a conduit.

The pressure value above 2.5 MPa occurs in high-pressure pipelines, from 1.6 to 2.5 MPa - in medium-pressure pipelines, and less than 1.6 MPa - in low-pressure pipelines. In addition to ground, underground, overhead and underwater pipelines, there are prefabricated or welded pipelines. The materials for them are also different: fiberglass, steel with a coating inside - anti-corrosion paintwork or polyethylene, as well as just steel. Corrosion of pipes in field pipelines for oil and gas is increased if acid treatments of the well or hydraulic fracturing are carried out. Associated water at the same time significantly reduces the pH in stagnation zones. Quite often, repair of field pipelines is required.

About metal corrosion

In order to reduce the corrosion of steel pipes, manufacturers have been conducting significant research and practical experiments in recent decades. Thus, a whole set of specifications was developed, where a number of important indicators are regulated, among which is the corrosion rate. The production of corrosion-resistant pipes began, for which steel is supplied with chromium, titanium, and vanadium additives. Clad, multilayer, combined and many other types of pipes are designed for existing oil fields, for the construction of trunk and field pipelines.

Service life increased, general corrosion decreased. But pipes have become much more expensive. At the same time, various organizations proposed for operation in the oil industry pipes made of plastic and fiberglass, as well as pure steel pipes.polyethylene coating internal and external, with only internal coating of varnishes and paints with anti-corrosion properties.

Code of Rules

The set of rules (hereinafter referred to as the SP) "Field pipelines" was withdrawn from the Technical Committee for Standardization (TK 465), further approved by the Ministry of Construction of the Russian Federation in 2016 and put into effect since June 2017. This document established requirements for industrial steel pipelines, and they also relate to the design, production and acceptance of work during the construction, reconstruction, overhaul of pipelines up to 1400 millimeters in diameter (inclusive). Overpressure should not exceed 32.0 MPa. The joint venture "Field pipelines" should apply to all field steel pipelines, in particular:

1. For gas and gas condensate fields - gas pipelines-looplines to the collection point or to the inlet valve located at the field site, that is, to sludge treatment plants, panel-polymer anchoring devices or to buildings with switching valves.

2. For gas collection manifolds - from well piping, raw gas pipelines, pipelines of unstable and stable gas condensate of any length.

3. For pipelines for supplying purified gas and inhibitor directly to wells and other facilities.

4. For pipelines under sewage pressure over 10 MPa, to supply them to wells and pump them into absorbing formations.

5. Forinhibitor lines.

6. For methanol lines.

7. For oilfields and oil and gas - flowlines from wells, except for sections on well pads, to transport the product up to metering stations.

8. SP 284 1325800 2016 "Field pipelines" also prescribes oil and gas pipelines for transporting well products from the metering unit to the oil separation point.

The document covers all types of pipelines used in the oil and gas industry, and the list is very long. Field pipelines for oil and gas, which transport oil together with gas, which is in a dissolved and free state, are classified as oil and gas pipelines, and oil pipelines - supplying degassed oil.

JV "Promyslovye Pipelines" rules do not apply to pipelines made of cast iron, composite and polymer materials, as well as to main pipelines for transporting commercial quality products and many other types. For example, pipes must have other qualities in order to transport products containing hydrogen sulfide, a product with a temperature above 100 degrees. These provisions do not apply to water conduits and technological pipelines inside the site.

Departmental building codes (BCH)

The construction of main and field pipelines is controlled by the VSN norms and applies to steel pipelines 1420 mm inclusive, according to these norms, the reconstruction and construction of a newequipment for operating and opening gas and oil fields. The distribution area is also controlled by design standards, including for underground storage facilities, where the medium is overpressured (no more than 32 MPa). VSN "Main and field pipelines" also consider flow lines that are needed for transportation from the well, where the diameter and length are regulated depending on technical calculations and well flow rates (from 75 to 150 millimeters in diameter of the flow line and no more than four kilometers in length).

Prefabricated collectors are designed to transport oil, which are laid from the metering plant to the pumping station or installation where oil is prepared. The diameter of prefabricated collectors is from 100 to 350 millimeters, the length can be more than ten kilometers. VSN "Field pipelines" set the standards for inhibitor pipelines that supply chemical reagents to wells (not only to wells, but also to other facilities where it is necessary within the framework of gas condensate, gas, oil and gas and oil fields. In the fields, water pipelines are also needed for construction and reconstruction of which must also be based on the Code of Practice and Departmental building codes.

Water is supplied to the injection wells to maintain pressure in the formation, after which the formation water is extracted along with oil, collected and discharged into aquifers. The construction of main and field pipelines also provides for this important element. Water pipelines are divided into main ones, starting frompumping stations on the second rise, to the supply ones, which connect the main water supply to the pumping stations of each cluster, to the distribution ones, which connect the injection wells to the cluster pumping stations.

Gas and gas condensate fields

At such facilities, field pipelines connect gas wells and gas treatment facilities with field distribution stations before gas enters the main gas pipeline, and also collect and utilize gas condensate with their help. They are divided into gas pipelines-loops, collector gas pipelines, condensate collection and field water pipelines. All this is being built and reconstructed strictly according to the rules that are presented in the VSN. The gas pipeline connects the well with a separator, where all unnecessary impurities are separated from the gas itself, and the gas is also dried and prepared for transportation.

There are group installations and separate gas separation points. The length of the plumes is from 600 meters to 5 kilometers, the diameter of the pipes is prescribed up to 200 millimeters. Field collectors for collecting gas must connect group preparation installations with gas distribution stations. The shape of the gas collection headers does not differ from other field gas pipelines that are used in oil fields. Condensate collectors are exactly the same as oil field collectors for collecting oil, they are used to transport gas condensate to a gas collection point or a gasoline production plant.

Construction of pipelines in Russia

Already in the eighties of the twentieth century in Russia everywhere they switched to the construction of sealed pressure systems, vacuum gas pipelines are not currently being designed at new fields. Gas pipelines, similar to flow lines, are divided according to their purpose - into supply lines, first of all. Further, similar to the prefabricated collectors for oil - prefabricated collectors for gas, and, finally, injection gas pipelines.

The shape also depends on the configuration of the field, on the size of the deposits and on the placement of booster stations and metering installations. In oil fields, the gas gathering system is named according to the shape of the collector: linear, if the collector is one line, radial, if the collectors are reduced to a single point, annular, if the collector goes around the oil structure over the entire area in a ring. The ring collector is usually designed with bridges for maneuverability and reliable operation.

Injection gas pipelines drive gas into the "cap" of the field from compressor stations in order to maintain reservoir pressure and extend the life of the well, as well as to supply it to wellheads through gas distribution booths, if the operation method is compressor. In the same way, gas is transported to processing plants and to gas fractionation plants for consumers.

Rules for the construction of field pipelines

Since these are capital engineering structures, that is, designed for a long service life and are intended for the transportation of oil products, gasand oil in an uninterrupted way from the place of production to facilities for complex treatment and places of entry into the main pipeline (as well as any other mode of transport, including river, sea and railway), many norms and rules are provided for construction. The main thing is GOST 55990 (2014) "Field pipelines" for oil and gas fields, where the design standards and rules for the application of this standard are set out in section 8. All changes are reported in the "National Standards" index. Amendments and changes in the official text are published monthly and from the Internet by the Federal Agency for Technical Regulation and Metrology on the official website.

GOST "Field pipelines" applies to reconstructed and new steel pipelines with a diameter of 1400 mm inclusive, where the excess pressure is not more than 32.0 MPa for oil, gas condensate and gas fields, as well as for underground storage facilities. The composition of field pipelines was mentioned above, this is how this standard operates. These are gas pipelines for gas condensate and gas fields, gas pipelines, gas gathering collectors, pipelines for stable and unstable gas condensate, for supplying an inhibitor and purified gas to wells and other facilities that require development, wastewater pipelines to wells (injection into absorbing formations), methanol pipelines.

GOST "Field pipelines" for oil and gas and oil fields is also described above. It's flickpipelines, oil and gas gathering, gas pipelines for the transport of petroleum gas, oil pipelines for the transport of gas-saturated or degassed anhydrous or watered oil, gas pipelines in the gas-lift method of oil production, gas pipelines for supplying to productive formations, pipelines for waterflooding, as well as waste and formation water disposal systems, oil pipelines for transport of commercial quality oil, gas pipelines for gas transportation, inhibitor pipelines, demulsifier pipelines at gas-oil and oil fields. GOST also provides for pipelines for underground storage facilities - between sites at facilities.

Laying pipelines

Field and main pipelines cross a huge number of a wide variety of natural and artificial barriers, which are called transitions - underwater, air or underground. Hydrogeological, natural, climatic conditions are also very different: rivers, ravines, gorges, karst-hazardous areas intersect. Sometimes only above-ground laying is the only option. The construction conditions are varied, and for each case, the norms and rules laid down in GOST are provided. Each site must meet operational, production, economic requirements.

The failure of any link will stop work along the entire length of the pipeline, which is hundreds and hundreds of kilometers. That is why all crossings are exclusively responsible structures. Pipes must be protected from both external and internal corrosion. All of them are tested for hydraulic resistance and strength,where the allowable pressure is calculated, taking into account field practice (most of the reference tables show the conditions for pumping water, and here the pipeline must work under more difficult conditions - pumping viscous mixtures and liquids).

Prefabricated pipelines - the main field collectors, which are laid to compressor stations and reservoir brands from individual or group prefabricated installations, play the most decisive role. Here, the terrain is extremely important if the collection scheme is separate-gravity. If the schemes are pressurized, the location of the main group collection installations is important. Diagnostics of pipelines shows that if there is no electrical and chemical protection, anode and cathode sections can form, where there are frequent removals of brown and dark brown corrosive products from under the overlapping turns of polymer insulation tapes.

Technological schemes of construction

Construction technologies cannot but be diverse, since transitions to other technological schemes dictate the variability of landscape characteristics: topographic, soil, hydrogeological, hydrological, and climatic characteristics change. If errors are made at any level, from design to project implementation, pipeline failure is likely to occur, often accompanied by fire and accidents. All problems can be divided into categorical and non-categorical. Pipelines and valves are subject to mandatory maintenance -Inspections are periodically carried out, the detected gas and oil leaks are eliminated. Walkdowns of pipelines where pipelines are laid near the ground are usually carried out in spring, autumn and at any time when a failure of the oil gathering and oil transportation network is suspected.

Since favorable climatic conditions practically do not exist anywhere in Russia, they are harsh everywhere, maintenance of any pipeline - field or main - is accompanied by complications. Oil and gas pipelines freeze in separate sections, the viscosity of the oil emulsion and oil in tanks at oil gathering plants in suction pumps increases. It is necessary to heat emergency areas, and only high-temperature water vapor is used, since an open flame will certainly cause a fire or explosion.

Internal corrosion of pipes is the most dangerous, it occurs because the products coming from wells are stratified: oil at the top - separately, formation water at the bottom - separately. And the water is highly mineralized, it contains a lot of various small particles that mechanically act on the lower part of the pipe, where furrows are formed along the length, a kind of groove. It is because of them that most of the pipeline failures occur. And such groove corrosion progresses very quickly: up to 2.7 millimeters per year.

Pipelines for the oil and gas field are mostly seamless pipes, which are much more durable because low carbon steel is used only of the best grades and is well heat treated. Oil pipesare made without thread, by electric welding. Pipelines must have fencing, fill edge or other designation of the boundaries of the site. The pipeline route is determined by the size and direction of the technical corridor, that is, the group laying of pipes for different or identical purposes must be streamlined. This includes the linear part, and transitions through obstacles of a natural or artificial plan, and shut-off valves, and pipe fixing devices, and electrochemical protection against corrosion.

To ensure the operational reliability of the designed pipelines at each stage of their use - from start-up and adjustment to dismantling and disposal, it is necessary to use the Code of Practice and not allow violation of the standards prescribed by GOST. It is for the purpose of improving the quality at the stages of design, construction and subsequent safe operation of field pipelines that these regulatory documents have been developed. First of all, it is necessary to minimize operational risks, adequately manage them: comply with all the requirements of the current technical regulations in accordance with standardization documents.